Free-flowing fertilizer compositions

ABSTRACT

The invention relates to free-flowing, powder fertilizer compositions characterized by having enhanced aqueous dissolution rates and being able to produce drift reduced aqueous agricultural spray medium. Specifically, the compositions are water-soluble, nitrogen-containing fertilizers physically blended with a guar gum drift reduction agent and a silicone defoaming agent either encapsulated or absorbed in an agricultural carrier.

This is a continuation of application Ser. No. 08/925,921, filed Sep. 9,1997, now U.S. Pat. No. 5,964,917 and a continuation of Ser. No.08/381,581 filed Jan. 13, 1995, U.S. Pat. No. 5,679,128.

FIELD OF THE INVENTION

The present invention relates to free-flowing fertilizer compositionswhich have enhanced aqueous dissolution rates. Specifically, thecompositions are water-soluble nitrogen-containing fertilizersphysically blended with a guar gum drift reducing agent and a siliconedefoaming agent. Most preferably, these unique compositions containdiammonium sulfate crystals blended with hydroxy propyl guar gum and astarch-encapsulated silicone defoaming agent.

BACKGROUND OF THE INVENTION

It is well recognized by the agricultural industry that it isadvantageous to the end-users to be able to formulate dry agriculturalchemicals such as fertilizers, pesticides, and/or adjuvants so that theycan be easily mixed with water and applied by means of a sprayingapparatus to a target area.

Mist, or the fine particles end of the droplet-size spectra in theseagricultural sprays, i.e., those less than about 150 microns indiameter, often reduce the effectiveness of the chemical deliveryprocess.

When the agricultural sprays are to be directed onto a specific target,the aerial spray or discharge delivery systems are typically mounted onairplanes, tractors, or ground rigs. However, as a result of spraydrift, much of the active chemical ingredients in a spray can berendered ineffective or lost because of the inability of the smalldiameter spray or mist particles to reach and impact upon the intendedtarget, i.e., the crop or field locus. While small droplets providebetter coverage of a target, they are more susceptible to drift thanlarger droplets. Spray drift represents a loss of agricultural chemicalfrom intended targets and thus results in dangers inherent in airground, and water pollution. Since off-target agricultural chemicals arewasted product and can have a negative environmental and economicimpact, especially if the agricultural spray medium contains fertilizerand most especially if the medium contains pesticide, it behoovessprayers to reduce this drift induced problem.

In many farming areas, soil is deficient in one or more of the naturalnutrients required for satisfactory growth of certain crops. As aresult, such crops do not give their optimum yield. When such conditionsexist, it is a common procedure to apply a fertilizer rich in therequired nutrients(s). The most common fertilizers in use today are thewater-soluble, nitrogen-containing fertilizers. Solutions of thefertilizers are usually applied to the crop locus via aqueous sprayingtechniques; and, as described above, this spraying process usuallyresults in the attendant production of fine mist and droplet drift.

One solution proposed in the art to reduce mist and chemical drift inaqueous agricultural sprays, such as those containing fertilizers, is toincorporate into the aqueous medium a viscosity-increasing amount of aguar gum or derivative of guar gum, specifically non-derivatized guargum, non-cationic derivatized guar gum, cationic guar gum, or mixturesthereof.

Although guar gum is often referred to as a cold water swelling polymer,guar gum hydrates in either cold or hot water give high viscositysolutions. The viscosity development depends, to a certain extent, onparticle size, pH, and temperature. Guar gum solutions are stable overthe pH range of 4.0-10.5. Aqueous solutions of non-derivatized guar gumare often somewhat cloudy because of the small amount of insoluble fiberand cellulosic material present.

All of the commercially important derivatives of guar gum are formed byetherification reactions. The hydroxy alkyl as well as carboxy methylderivatives tend to be much clearer and more stable than thenon-derivatized guar gum. Improved clarity results from thederivatizations and solubilizations of insoluble seed impurities.

However, the aqueous hydration of dry, water-soluble polymers such asguar gum and/or its derivatives in an aqueous agricultural spray mediumin order to realize drift reduction properties can often be an arduousand frustrating task for the end-user.

Insufficient dispersion of powdered guar gum caused most often by thetoo rapid addition of the powder to the aqueous medium or insufficientagitation of the medium during the guar gum addition process of timesresults in agglomeration or lumps of guar gel. The lumps of guar gel,“fish-eyes”, or other inhomogeneity of the mixture can result indifficulty in spraying and loss of drift control. These gel lumps notonly cause a lowering of the overall concentrations of dissolved guargum in the spray medium, and, thus, a reduced drift control of themedium, but also result in medium that will not flow or be readilypumpable and a plugging of the spray nozzle holes. The agglomeration orgellation can be reduced in many cases by adding the guar gum to theaqueous system very slowly with vigorous agitation. Slow addition,however, substantially reduces the efficiency and speed of the end-usersprocesses. For the above reasons, agricultural end-users, such asfarmers, continue to desire a fast, effective and simple way ofincorporating guar gum and/or its derivatives into their aqueoussystems.

By physically pre-blending water-soluble nitrogen-containing fertilizersuch as diammnonium sulfate with any of the above-described guar gum orguar gum derivatives such as hydroxy propyl guar, formulators canpresent to the agricultural end-user a dry system that can be easilyhandled in that, for example, bulky liquid containers do not have to bestored, recycled, etc. and the end-user need not be concerned aboutensuring that the weight ratios of fertilizer to drift reduction agentare correct.

Applicants have discovered that, serendipitously, the pre-blendedcomposition of water-soluble nitrogen-containing fertilizer and the guargum drift reduction agent has the added advantages of enhancing theuniform dispersion and hydration of the guar agent by significantlyreducing the agglomeration and gellation problems inherent in theaqueous hydration of powdered guar and its derivatives. Although notwishing to limit the scope of this discovery, the inventive scope to beset forth and determined solely by the claims, it is believed that thewater-soluble, nitrogen-containing fertilizers, such as diammnoniumsulfate which tend to be crystalline, and, thus, are of a higher densitythan the drift reduction agents, at the outset, initially provide asolid barrier which physically separates the guar gum agent particles,i.e., provides a dilution effect. Secondly, by being of a relativelyhigher density, the fertilizer crystals tend to quickly pull the guargum agent particles toward the bottom, i.e., down through the aqueousagricultural medium. The above two effects apparently ensure that amaximum surface area of the guar gum agents remains exposed to theaqueous medium and, thus, the overall hydration rate is enhanced.

Although the pre-blends of water-soluble, nitrogen-containing fertilizerand guar gum drift reduction agent are a decided improvement in the artand provide significant and unexpected advantages to the end-users asdescribed above, problems still occur in actual field use of theseblends when end-users, such as farmers, attempt to add the dry blend toa medium which may already contain an agricultural chemical or adjuvantformulation. This is because pesticides and/or adjuvants routinelycontain surfactants which generate foam under agitation conditionsprevalent in typical spray application equipment. With the presence offoam during the addition of the dry blends, the dispersion of thefertilizer blends is reduced and gelling and agglomeration problemsoften return.

Accordingly, users of water-soluble, nitrogen-containing fertilizerscontinue to desire a dry blend containing these fertilizers that can beincorporated into aqueous spray mixtures rapidly and completely toachieve drift reduced, sprayable agricultural media without theformation of agglomerates, gels, or clumps and which can be readily andsafely handled in dry form.

SUMMARY OF THE INVENTION

This invention is a free-flowing fertilizer composition comprisingwater-soluble, nitrogen-containing fertilizer; a guar gum driftreduction agent; and a silicone defoaming agent either encapsulated orabsorbed in an agriculturally acceptable carrier; preferably, alsocontaining an oil or nonionic surfactant dedusting agent; and theprocess for preparing same.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are graphical representations of hydration ratecomparisons of firstly, a hydroxypropyl guar gum composition versus theguar gum admixed with a fertilizer, and secondly, the latter blendversus the blend with a silicone defoaming agent admixed.

DETAILED DESCRIPTION OF THE INVENTION

In describing the preferred embodiment, certain terminology will beutilized for the sake of clarity. Such terminology is intended toencompass the recited embodiment, as well as all technical equivalentswhich operate in a similar manner for a similar purpose to achieve asimilar result.

The instant invention is a free-flowing fertilizer composition whichwill rapidly and completely dissolve in water to produce a drift reducedagricultural spray media. A preferred embodiment of this inventionincorporates a dedusting agent. Another aspect of this invention is theprocess for preparing the aforementioned powder composition.

The essence of the invention lies in the discovery that the enhancedhydration rates and the reduction of agglomeration and gellationrealized by physical pre-blends of water-soluble, nitrogen-containingfertilizers and the guar gum drift reduction agents can be sustainedeven when the blend is introduced rapidly into a highly agitated,aqueous agricultural medium if a silicone defoaming agent, eitherencapsulated or absorbed in an agriculturally acceptable carrier, isincorporated therein.

The water-soluble, nitrogen-containing fertilizer of particular interestin this invention is ammonium sulfate (sometimes called diammoniumsulfate) which has the formula (NH₄)₂ SO₄, but other fertilizercompounds such as urea; other ammonium salts, e.g., ammonium chloride,or ammunonium phosphates; nitrates, e.g., ammonium nitrate, calciumnitrate, sodium nitrate, or potassium nitrate; or substituted ureas,e.g., urea-aldehyde condensates or methylene ureas may also be employed.

The fertilizer component will often also contain a source of availablephosphorous, e.g., in the form of an inorganic phosphate such asammonium phosphate or a potassium phosphate. A source of availablepotassium may also be included, e.g., as potassium nitrate, a potassiumphosphate, potassium sulfate, or potassium chloride.

The fertilizer component may also include trace elements necessary forsatisfactory crop growth, which are sometimes deficient in the soil.Examples are zinc, iron, copper, cobalt, molybdenum, and manganese. Suchtrace elements may be present as their salts, or as anions such asmolybdate or as a complex. For example, iron may be present as a complexwith ethylenediamine tetraacetic acid.

The water-soluble, nitrogen-containing fertilizers of the instantfree-flowing compositions should be from about 87.50 to about 99.80weight percent of the composition; most preferably from about 92.0 toabout 97.0 weight percent based on the total weight of the composition.

Typical polymers used as drift reduction agents include thepolyacrylamides the polyethylene oxides, the poly (vinyl pyrrolidones),and natural gums such as guar gum and/or its derivatives. Currently, thepolyacrylamides are the agricultural industry spray tank additive, driftreduction standard. However, synthetics such as the polyacrylamides,have inherent drawbacks. For example, they are usually distributed inorganic carriers which limits the dispersibility and additionally canpresent a volatile organic component problem for the end user. Thepolymers themselves are essentially non-biodegradable and, therefore, itwould be highly desirable from an environmental viewpoint to reducetheir usage. Furthermore, these high molecular weight synthetic polymersare extremely sensitive to shear stresses. The high shear degradation ofthe synthetic polymers often realizes a significant decrease in solutionviscosity over time which results, in spray processing, in a lesseningof the droplet-size distribution control effects.

In summary, synthetic polymers, such as the polyacrylamides, haveseveral major characteristics that are not conducive to ease of use orreliable efficiency: difficult dispersibility; low biodegradability; andshear sensitivity.

Natural guar and its derivatives, under controlled conditions; functionas excellent drift reducing agents with essentially none of theabove-identified disadvantages associated with the synthetic agents suchas the polyacrylamide agents.

Guar gum is the refined endosperm of the legume seed of (L.) Taub., aplant which physically resembles the soy plant. The gum is a pure foodvegetable colloids recognized by the agricultural, chemical and foodformulation industry for many years as having excellent thickening,film-forming and stabilizing properties.

Functionally, non-derivatized guar gum is a cold water swelling,nonionic polysaccharide which develops and maintains its properties overa wide pH range. The guar polysaccharide is a complex carbohydratepolymer composed of essentially a straight chain of mannose units withsingle-membered galactose branches; chemically classified as apolygalactomannan.

Guar solutions are prepared by sifting dry gum into a vigorouslyagitated tank of water and permitting the gum to hydrate. Higher watertemperatures can shorten the hydration time so long as the heating isnot so prolonged or excessive as to degrade the polymer.

The nature of guar allows almost constant viscosity for a given solutionconcentration over the pH range of 3-10. Above pH 11, a lower viscosityresults from the decreased ability of the gum to hydrate. The optimumhydration range occurs between pH 5 and 8. This unusual compatibility ofguar over the 3-10 pH range is attributed to the nonionic nature of themolecule.

Etherification and esterification reactions are made on the guarhydroxyl functionalities. The C₆ hydroxyl position is the most reactiveposition for etherification, for example, with propylene oxide, but thesecondary hydroxyls are also probable sites.

Principle etherification reactions are carboxymethylation viamonochloroacetic acid, hydroxyalkylation via ethylene oxide or propyleneoxide, and quaternization with various quaternary amine compoundscontaining reactive epoxide or chloride sites. Anionic and cationicsites modify the way the guar molecule interacts with inorganic salts,hydrated cellulosic and mineral surfaces, and organic particulates.

In general, the hydroxyalkyl ethers of polygalactomannans are preparedby reacting the polygalactomannans with alkylene oxides under basicconditions. In U.S. Pat. Nos. 3,723,408 and 3,723,409, guar flour isreacted with alkylene oxides in the presence of water and sodiumhydroxide. The reaction product is then neutralized with acid, washedwith an alcohol-water mixture, and is then dried and ground. In U.S.Pat. No. 3,483,121, the polygalactomannans and the alkylene oxides arereacted under basic conditions with small amounts of water and largeramounts of water miscible or water immiscible organic solvents.

Specific hydroxyalkylating agents include ethylene oxide, propyleneoxide-1,2; butylene oxide-1,2; hexylene oxide-1,2; ethylenechlorohydrin; propylene clorohydrin; and epichlorohydrin.

Hydroxypropylation increases the gum's solubility, resulting in aproduct which hydrates rapidly, regardless of water temperature. Bothhydroxyalkyl and carboxymethyl derivatives typically form clearersolutions than standard non-derivatized guar gum and also hydroxyalkylderivatives resist thermal degradation better than non-derivatized guar.Hydroxypropyl guar gum is particularly useful as a flow modifier andfriction reducing agent and is the most preferred derivatized guar gumof this invention.

Carboxyalkyl ethers and mixed carboxyhydroxyalkyl ethers ofpolygalactomannans are described in U.S. Pat. Nos. 3,740,388 and3,723,409, respectively. These derivatives are made by reacting thepolygalactomannan with the derivatizing agents (halofatty acid andalkylene oxide) in a water-alcohol mixture followed by washing withwater-alcohol mixtures.

Specific carboxyalkylating agents include chloroacetic acid,chloropropronic acid, and acrylic acid.

Carboxymethylation introduces an anionic function to the polymer chainand further increases the solubility of guar gum. Carboxymethylhydroxypropyl guar gum is exceptional in its ability to suspendundissolved solids.

Other derivatives of polygalactomannans are described in such patents asU.S. Pat. No. 2,461,502 (cyanoethyl ethers), U.S. Pat. No. 4,094,795(dialkylacrylamide ethers) and U.S. Pat. No. 3,498,912 (quaternaryammonium alkyl ethers). In the described processes, the reactions areconducted in water-organic solvent mixtures and the reaction productsare washed with solvents of water solvent mixtures. Specific quaternaryammonium alkylating agents are such agents as 2,3-epoxypropyltrinethylammonium chloride, 3-chloro-2-hydroxypropyl trimethylammoniumchloride and the like.

Other agents that can react with the hydroxyl groups of thepolygalactomannans to form ether groups are, for example, alkylatingagents which include methyl chloride. methyl bromide, ethyl chloride,ethyl iodide and isopropyl chloride; aminoalkylating agents; such asaminoethyl chloride, aminopropyl bromide, and N,N-dimethylaminopropylchloride; ethylenically unsaturated group containing agents which reactthrough Michael addition with hydroxyl groups such as acrylamide,methacrylamide, acrylonitrile, methacrylonitrile, acrylic acid, sodiumacrylate and, in fact, any of the polymerizable monomers which containone ethylenically unsaturated polymerizable group.

The term “derivatized guar” is meant to include any of the abovedescribed derivatized guar gum products.

Non-derivatized guar gum, derived from a nitrogen-fixing, renewableresource, is a versatile, environmentally friendly, highly biodegradablepolymer. Derivatized guar gums are slightly less sensitive to biologicaldegradation, as the molecules are less suitable as food for commonorganisms.

The drift reduction agent of this invention which is selected from thegroup consisting of non-derivatized guar gum, non-cationic derivatizedguar gum, cationic guar gum, and mixtures thereof is from about 0.01 toabout 12.49 weight percent; preferably from about 0.01 to about 10.0weight percent; and most preferably from about 3.0 to about 7.0 weightpercent based on the total weight of the powder composition.

A defoaming or antifoaming agent is a material which, when added in lowconcentration to a frothy or foaming liquid, controls or reduces thefoaming problem. The agent equilibrates the rate of foam collapse withthe rate of foam formation. The term “defoaming” implies breaking apre-existing foam whereas “antifoaming” indicates prevention of theformation of that foam. Such distinctions can call for different productperformance characteristics.

Whereas a defoamer is expected to exhibit rapid knockdown of a foam,longevity of action might be the key requirement in many antifoamapplications. Many, if not most, applications require both preventativeand control functions, and, in practice, the same types of materials areused for both antifoaming and defoaming. Thus, the general termdefoaming agent is meant to encompass both types and degrees of action.

The physicochemical control of foam is most obviously useful forincreasing the holding capacity of vessels, improving filtration,dewatering, washing and drainage of various types of suspensions,mixtures or slurries. The term physicochemical is used, rather thanchemical for current theory suggests that although dewetting helps thinthe bubble film and promote instability, foam collapse may be due to thedirect mechanical shock of the event. Although the use of vegetable andmineral oil defoaming agents have been known for some time, most highlyeffective defoaming agents today are complex, formulated and proprietaryspecialty chemicals. In addition to the reduction of foam and itsassociated features such as rate of foam knockdown and the persistenceof the effects, other frequently needed application requirements ofthese specialty materials include adequate shelf life, absence ofadverse effects on the medium or target being treated, ease of handling,lack of toxicity to formulators and end-users, environmentalacceptability and cost-effectiveness.

The polysiloxane based defoaming agents have been found to be thecompositions of choice for the expectedly outstanding results achievedby the granular fertilizer compositions of the instant invention.

Polysiloxanes, despite their considerable defoaming effectiveness innon-aqueous systems, show little foam-inhibiting activity in aqueoussurfactant solutions. However, when substituted and compounded withhydrophobic silica, highly effective aqueous defoamers result.

The three most common ways of preparing the hydrophobic silica are tospray silica with silicone oil and heat at 250-350° C.; to treat silicawith organochlorosilane vapors in an autoclave; and to disperse silicain a silicone oil at elevated temperatures. Hydrophilic silica can alsobe produced by treatment with various alcohols, fatty amines, andhydrocarbon waxes.

The polysiloxanes used to prepare the defoaming agents of this inventioncan be alkyl, alkoxy, or aryl substituted. Cyclic polysiloxanes andhydroxylated polysiloxanes can also be utilized.

The preferred silicones used to prepare the defoaming agents of theinstant compositions are the polydimethylsiloxanes having a molecularweight in the range of from about 200 to about 200,000 and a viscosityin the range of from about 20 to about 2,000,000 centistokes, preferablyfrom about 500 to about 50,000 centistokes at 25° C. The polymers aregenerally end-blocked with either timethylsilyl or hydroxyl groups, butother end-blocking groups are also suitable. The polymers can beprepared by various techniques such as the hydrolysis and subsequentcondensation of dimethyldihalosilanes, or by the cracking and subsequentcondensation of dimethylcyclosiloxanes.

The preferred silicone defoaming agents are prepared by combining thepolydimethylsiloxane with particulate silica. Such combinations ofpolydimethylsiloxane and silica can be prepared by affixing the siliconeto the surface of the silica, for example, by means of the catalyticreaction disclosed in U.S. Pat. No. 3,235,509.

Foam regulating agents comprising mixtures of silicone and silicaprepared in this manner preferably comprise silicone and silica in asilicone:silica ratio of from 20:1 to 200:1, preferably about 25:1 toabout 100:1. The silica can be chemically and/or physically bound to thesilicone in an amount which is preferably about 0.5% to 5% by weight,based on the silicone. The particle size of the silica employed in suchsilica/silicone foam regulating agents is finely divided and shouldpreferably be not more than 100 millimicrons, preferably from 10millimicrons to 20 millimicrons, and the specific surface area of thesilica should exceed about 50 m²/g.

It is most preferable that the milky liquid silicone/silica defoamingagent be in a relatively dry solid form for incorporation into thefree-flowing granular fertilizer compositions of this invention. To thatend, the most preferred embodiment of the instant invention is onewherein the liquid silicone/silica defoaming compound is eitherencapsulated by an agriculturally acceptable material or absorbed in anagriculturally acceptable solid carrier. The encapsulating material ispreferably a coating that preserves the integrity of the defoamingagent, but allows rapid disruption when in contact with the aqueousmedia. An example of such an encapsulating material is starch. A starchencapsulated, silicone/silica proprietary antifoam composition iscommercially available from Rhone-Poulenc under the trademark RHODORSILEP-6703. That the starch encapsulated defoaming agents work so extremelywell in this invention is particularly surprising in view of the factthat the presence of starch foam presents a considerable defoamingchallenge in many industrial processes.

Relatively solid defoamers also can be produced by absorbing the liquidsilicone/silica defoaming agents into inorganic solid sorbent carrierssuch as clay, finely ground haolin, talcum, chalk, limestone,attapulgite, pumice, precipitated silica, pyrogenic and fumed silica,attaclay, dolomite, diatomaceous earth, etc. Water-soluble inorganicsorbent carriers such as sodium sulfate, sodium carbonate, calciumcarbonate, or sodium tripolyphosphate can also be used.

The silicone defoaming agent in this invention is from about 0.01 toabout 12.49 weight percent; preferably from about 0.01 to about 2.50weight percent; most preferably from about 0.1 to about 1.0 weightpercent based on the total weight of the fertilizer composition.

Handling of dry powder or granule compositions can be hampered by thetendency of these compositions to generate undesirable dust. The dustassociated with dry, particulate water-soluble fertilizers and polymerscan present the same conventional handling problems as are encounteredwith similar particulate materials—one major concern is the possibilityof dust explosions.

In order to overcome the dusting and its potential problems, dustinhibiting, i.e., dedusting agents are usually added. Dedusting agentscan have electrostatic binding characteristics, but more typically areliquid and/or tacky compounds. Also, in the instant invention, it iscontemplated that solid or semi-solid dedusting agents can be meltedprior to blending with and/or being sprayed upon the dry solidcomponents of the fertilizer compositions.

Suitable dedusting agents include, for example, nonionic surfactants,cyclic hydrocarbons, e.g., decalin and tetralin; phthalic acid dialkylesters; mineral oils, especially mineral oils with a boiling range offrom 130° to 300° C. as well as partially sulfonated mineral oils;silicone oil polymers and copolymers; especially the silicone-containingsurface active agents; and mixtures thereof.

Although simple oils such as mineral or paraffin oils functionadequately as dedusting agents, the dedusting agents that also havewetting characteristics such as the nonionic surfactants and nonionicsilicone surfactants are much preferred. The most preferred nonionicsurfactants are the following:

A) Amides such as:

i) Alkanolamides of the formula—

wherein R′ and R″ each can be —H, —CH₂CH₂OH, or

ii) ethoxylated alkanolamides of the formula—

iii) ethylene bisamides of the formula—

B) Esters such as:

i) fatty acid esters of the formula—

ii) glycerol esters of the formula—

iii) ethoxylated fatty esters of the formula—

iv) sorbitan esters of the formula—

v) ethoxylated sorbitan esters of the formula—

C) Ethoxylates such as:

i) alkylphenol ethoxylates of the formula—

ii) alcohol ethoxylates of the formula—

R—O—(CH₂CH₂O)_(n)H;

iii) tristyrylphenol ethoxylates of the formula—

iv) mercaptan ethoxylates of the formula—

R—S—(CH₂CH₂O)_(n)H;

D) End-capped and EO/PO block copolymers such as—

i) alcohol alkoxylates of the formula—

ii) ethylene oxide/propylene oxide block copolymers of the formula—

iii) copolymers of the formula—

iv) chlorine capped ethoxylates of the formula—

R—(OCH₂CH₂)_(x)Cl;

 and

v) tetra-functional block copolymers of the formula—

 wherein

R is a fatty alkyl group, preferably a C₆-C₂₂ fatty alkyl group, mostpreferably a C₈-C₁₈ fatty alkyl group;

R₁ is —H or a fatty alkyl group, preferably —H or a C₆-C₂₂ fatty alkylgroup, most preferably —H or a C₈-C₁₈ fatty alkyl group;

x, x¹, y, y¹ and n are each independently moles of ethylene oxidepreferably 1 to 300; most preferably 1 to 150; and

m, m¹, l and l¹ are each independently moles of propylene oxide,preferably 1 to 300; most preferably 1 to 150.

Also preferred as dedusting agents are the silicone containing surfaceactive agents. This encompasses any and all silicone containingmaterials which both includes one or more hydrophobic groups anddemonstrates surface active properties. Particularly preferred are theuse of silicone polymers which include alkoxylate groups such asethylene oxide, propylene oxide, and mixtures thereof. Examples ofsilicone surface active agents which may be selected for use in thepresent composition are dislcosed in the following patent documents:U.S. Pat. Nos. 5,104,647, 5,017,216, 5,145,978, 5,145,977 and WO94/22311. To the extent necessary for completion, these patents arehereby expressly incorporated by reference.

If incorporated into the fertilizer composition of this invention, thededusting agent is from about 0.005 to about 15.0 weight percent;preferably from about 0.01 to about 2.5 weight percent; most preferablyfrom about 0.1 to about 1.0 weight percent based on the total weight ofthe fertilizer composition.

This invention is demonstrated in the following example(s), which areillustrative; not intended to be limiting; and wherein all parts,percentages, etc., are by weight.

EXAMPLE I

Diammonium sulfate crystals and a derivatized guar (AgRHO DR 2000 whichis a trademark of Rhone-Poulenc for a proprietary hydroxy propyl guarblend) are blended together and milled to a fine powder. IGEPAL CO-630,a trademark of Rhone-Poulenc for an ethoxylated (8 EO) nonyl phenolnonionic surfactant is sprayed onto the powder blend with continuousmixing. The composition of the final dry, free-flowing powder,identified as Blend 1, is as follows:

Blend 1 Diammonium Sulfate 94.10 weight percent DR 2000 5.60 weightpercent IGEPAL CO 630 0.30 weight percent 100.00 weight percent

To a first 1500 ml beaker containing 500 grams of tap water is sprinkleda sufficient amount of Blend 1 powder to achieve a 0.1% guarweight/weight mixture of guar and tap water. To a second 1500 ml beakercontaining a like amount of tap water is sprinkled a sufficient amountof AgRHO DR 2000 guar composition to also achieve a 0.1% guarweight/weight mixture of guar and tap water.

The rate of hydration of the polymer/water mixture is then monitored bymeasuring the increase in viscosity of the mixture over time using aBrookfield rheometer interfaced to a Compaq 486 personal computer andequipped with an RV-2 spindle at 55 rpm. Viscosity data is collectedevery 45 seconds for a total of 6 minutes. During this hydration period,care is taken to maintain the polymer particles in suspension byphysically stirring the mixture after the third, sixth, ninth, andtwelfth measurements. Each formulation is evaluated four times asdescribed above. The four replicates for each formulation are averagedat each time interval and plotted as a single hydration curve.

The results are as indicated in Table I below and are graphicallydepicted in FIG. 1.

TABLE I Apparent Hydration Time (Minutes:Seconds) Viscosity, cps 0 DR2000 Blend 1 1:20 15.7 18.0 1:40 15.3 18.1 2:00 14.7 18.5 2:20 14.1 19.82:40 14.0 20.6 3:00 14.2 21.0 3:20 — 21.2 3:40 15.0 22.0 4:00 15.0 22.24:20 15.2 23.0 4:40 15.3 25.3 5:00 15.5 24.4 5:20 15.8 24.2 5:40 15.724.1 6:00 15.8 24.0

The above tests illustrate that the presence of the water-soluble,nitrogen-containing fertilizer crystals, i.e., the diammnonium sulfateresults in a significant enhancement of the hydration of the hydroxypropyl guar gun drift reduction agent.

EXAMPLE II

In this example, diammonium sulfate fertilizer crystals and a hydroxypropyl guar gum (AgRHO DR 2000) drift reduction agent are blendedtogether and milled to a fine powder. A starch encapsulated siliconedefoaming agent (RHODORSIL EP 6073—a trademark of Rhone-Poulenc) issubsequently blended into the milled powder. Finally, a dedusting agent(IGEPAL CO-630) is sprayed upon the powder blend with continuous mixing.The composition of the final dry, free-flowing, dust reduced fertilizercomposition, identified as Blend 2 is as follows:

Blend 2 Diammonium Sulfate 93.8500 weight percent DR 2000 5.6000 weightpercent IGEPAL CO-630 0.3000 weight percent Starch 0.1875 weight percentSilicone Defoamer 0.0625 weight percent 100.0000 weight percent

To a one quart, wide mouth jar containing 498.5 grams of tap water isadded AgRHO FM-3800 (1 gram). The AgRHO FM-3800 (a trademark of RhonePoulenc) is a complex proprietary composition of surfactants designed tocreate a very stable foam. The jar is capped and shaken by hand brieflyto generate foam. All the water and 600 ml of the resulting foam istransferred to a first 1500 ml beaker. A second beaker is prepared asabove.

Into the first beaker is sprinkled a sufficient amount of Blend 2 powderto achieve a 0. 1% guar weight/weight mixture of guar gum and tap water.To the second beaker is sprinkled a sufficient amount of Blend 1 to alsoachieve a 0.1% weight/weight mixture of guar gum and water. After a 30second period, the remaining foam is removed from each beaker tofacilitate the measurement of hydration rate.

The rate of hydration is measured as in Example 1.

The results are as indicated in Table II below and are graphicallydepicted in FIG. 2.

TABLE II Apparent Hydration Time (Minutes:Seconds) Viscosity, cps 0Blend #1 Blend #2 0:30 9.4 9.7 1:30 9.8 9.9 2:30 9.9 10.0 3:00 10.3 10.93:30 10.6 11.1 4:30 10.9 11.5 5:00 11.2 11.8 6:00 11.3 12.2 6:30 11.212.4 7:30 11.7 13.1 8:00 11.6 12.8 9:00 11.8 13.0 9:30 12.2 13.5 10:30 12.2 13.4 11:00  12.0 13.7

The above tests illustrate that when the encapsulated silicone defoamingagent additive of the instant invention is incorporated intowater-soluble, nitrogen-containing fertilizer—guar gum drift reductionagent compositions, significant enhancement of the hydration of thedrift reduction agent occurs.

The rate of application of the powder blend will be selected in relationto the intended fertilizer effect, taking into account the compositionof the powder, the crop, the nature of the soil, the weather, etc.

While the invention has been described with respect to the specificembodiments, it should be understood that they are not intended to belimiting and that many variations and modifications are possible withoutdeparting from the scope of this invention.

What is claimed is:
 1. A free-flowing powder fertilizer compositioncomprising: i) about 87.50 to about 99.80 weight percent of awater-soluble nitrogen-containing fertilizer; ii) about 0.01 to about12.49 weight percent of a drift reduction agent, wherein the driftreduction agent is selected from the group consisting of non-derivatizedguar gum, non-cationic derivatized guar gum, cationic guar gum, andmixtures thereof; and iii) about 0.01 to about 12.49 weight percent of adefoaming agent, wherein the defoaming agent is either encapsulated orabsorbed in an agriculturally acceptable carrier, and wherein all weightpercents are based on the total weight of the free-flowing powderfertilizer composition.
 2. The composition according to claim 1 whereinthe water-soluble nitrogen-containing fertilizer comprises diammoniumsulfate.
 3. The composition according to claim 1 wherein thewater-soluble nitrogen-containing fertilizer is urea, ammonium salt,nitrate, or substituted urea.
 4. The composition according to claim 1wherein the non-cationic derivatized guar gum is hydroxy propyl guar gumor carboxy methyl hydroxy propyl guar gum.
 5. The composition accordingto claim 1 wherein the defoaming agent is a vegetable oil or a mineraloil defoaming agent.
 6. The composition according to claim 1 wherein thedefoaming agent comprises a polysiloxane-based defoaming agent.
 7. Thecomposition according to claim 6 wherein the polysiloxane-baseddefoaming agent is a starch encapsulated polydimethylsiloxane.
 8. Thecomposition according to claim 1 further comprising about 0.005 to about15 weight percent of a dedusting agent.
 9. The composition according toclaim 8 wherein the dedusting agent is a nonionic surfactant, cyclichydrocarbon, phthalic acid dialkyl ester, mineral oil, silicone oilpolymer, silicone oil copolymer, or a combination thereof.
 10. Thecomposition according to claim 8 wherein the dedusting agent comprises anonionic surfactant.
 11. The composition according to claim 8 whereinthe dedusting agent is a nonyl phenol ethoxylate.
 12. The compositionaccording to claim 1 wherein the agriculturally acceptable carriercomprises an inorganic solid sorbent carrier.
 13. The compositionaccording to claim 12 wherein the inorganic solid sorbent carrier isclay, finely ground haolin, talcum, chalk, limestone, attapulgite,pumice, precipitated silica, pyrogenic silica, fumed silica, attaclay,dolomite, diatomaceous earth, or a combination thereof.
 14. Thecomposition according to claim 1 wherein the agriculturally acceptablecarrier comprises a water-soluble inorganic sorbent carrier.
 15. Thecomposition according to claim 14 wherein the water-soluble inorganicsorbent carrier is sodium sulfate, sodium carbonate, calcium carbonate,sodium tripolyphosphate, or a combination thereof.
 16. A method foragricultural fertilization, the method comprising the steps of: a)providing a free-flowing powder fertilizer composition comprising: i)about 87.50 to about 99.80 weight percent of a water-solublenitrogen-containing fertilizer; ii) about 0.01 to about 12.49 weightpercent of a drift reduction agent, wherein the drift reduction agent isselected from the group consisting of non-derivatized guar gum,non-cationic derivatized guar gum, cationic guar gum, and mixturesthereof, and iii) about 0.01 to about 12.49 weight percent of adefoaming agent, wherein the defoaming agent is either encapsulated orabsorbed in an agriculturally acceptable carrier, and wherein all weightpercents are based on the total weight of the free-flowing powderfertilizer composition; and b) applying the free-flowing powderfertilizer composition to agriculture.
 17. The method according to claim16 wherein the water-soluble nitrogen-containing fertilizer comprisesdiammonium sulfate.
 18. The method according to claim 16 wherein thewater-soluble nitrogen-containing fertilizer is urea, ammonium salt,nitrate, or substituted urea.
 19. The method according to claim 16wherein the non-cationic derivatized guar gum is hydroxy propyl guar gumor carboxy methyl hydroxy propyl guar gum.
 20. The method according toclaim 16 wherein the defoaming agent is a vegetable oil or a mineral oildefoaming agent.
 21. The method according to claim 16 wherein thedefoaming agent comprises a polysiloxane-based defoaming agent.
 22. Themethod according to claim 16 wherein the free-flowing powder fertilizercomposition further comprises about 0.005 to about 15 weight percent ofa dedusting agent.
 23. The method according to claim 16 wherein theagriculturally acceptable carrier comprises an inorganic solid sorbentcarrier.
 24. The method according to claim 16 wherein the agriculturallyacceptable carrier comprises a water-soluble inorganic sorbent carrier.